Process for working zinc



' Patented Cet.4 2, 192.

f lr sa WALTER MARCUS TOWNE, OF NEW" YORK, N. Y., ASSIGNOR, VABY MESNE ASSIGN- MENTS, To n. w. Buss COMPANY, or BROOKLYN, new Yonx, a oonronArIoN or DELAWARE.

PROCESS FOB WORKING ZINC.

Application iled July 27, 1925. Serial No. 46,482.

` This invention relates to the production of tubular zinc articles, especially in the form of cups or containers, by extrusion.

The resent invention follows the method claimed) in my Patent No. 1,492,230, granted April 29, 1924,'a'nd constitutes a specific improvement thereon.

According to the process of that patent 4ablank of zinc, preferably soft zinc practically A free from grain formation and preferably zinc having a lead content not exceeding 0.6 per cent and a cadmium content not exceeding 0.5 per cent, is subjected to pressure between male and female dies and extruded through the contracted annular space surrounding the male die in the direction opposite to the movement of the male die, and while at a temperature approximating 150J C. The present invention is based upon a later discovery and in-` 2.volves essentially the extrusion at a considerably higher temperature approximating 260 to 300 whereby certain practical advantages are attained as compared with the process specifically set forth in my said prior patent, as will be explained.

In practising 'the process of the present invention I may use the same dies and tools as illustrated in my said Patent No. 1,492,230 and follow generally the same procedure with respect to the selection of the zinc and the preparation of the Zinc preparatory to the Aextrusion process. For these conditions it is sufficient to make reference to said patent, it being unnecessary here to repeat the detailed discussion and directions therein contained.

The only difference made according to my present invention is in the temperature at which the extrusion is performed. This, instead of being a temperature approximating as closely as possible to 150 C3?, as stated in m said patent, is a temperature materially above 150 C. and preferably approximating 260 to 300 C.

For the better understanding of my present improvement I refer to the accompanying drawin the single figure of which is a diagram s owing the plasticityy curve for zinc extrusion, that is to say,the pressures required at various temperatures for extruding zinc battery cups as shown in said Patent No.

1,492,230 having au external diameter of 1.25 inch and side walls .014 inch thick. In this curve it will be noted that the point a is the one corresponding to the temperature of 150 frapidity and C. stated aspreferable in my aforesaid patent. Below this temperature the pressure required for extrusion builds up with great soon becomes so great as tobe rapidly destructive to the die surfaces, thus causing awasteful abrasion of the dies and also requiring av high expenditure of power to operate the extrusion press. The point b indicates the temperature of 260 to 300 C., at

which I preferably perform the extrusion according to the present invention. This elevation of temperature is accompanied by a diminution in pressure owing to the greater plasticity of the zinc at this higher temperature. Working at this temperature accomplishes an important economy in power, and also a very serious advantage in the greater endurance of the dies. By reason of the more free How of the metal there is apparently and probably some improvement in the quality of the extruded cup.

I have even successfully worked at temperatures somewhat higher than 260 to 300 C., and even as high as 34.0 to 350 C.. but these higher temperatures have no sufficient advantage in facilitating the operation, and are subject to the disadvantage that they approach too closely to that at which the temper of the dies, .or at least that of the male die or punch, is liable to be affected. As the dies for such work are quite expensive, it is of great practical importance to give them the longest ossible life, and any sOftening of the working faces of the dies due to the drawing oftheir temper causes their rapid deterioration. To avoid this, the temperature of the zinc while being worked should not be carried so high as to cause this destructive edect upon the dies.

My present invention very materially increases the economy of production of zinc battery cups and other similar zinc products by extrusion according to the process claimed in my said patent. This economy is due to 'more ra id operation, giving a higher output; to re uced cost for power; and to prolonged life' of the dies owing to their operatin on the zinc in a condition which imposes ess strain on the working faces of the At the time whenV I applied for my said patent I stated that at higher temperatures (than 150 C.) there is a decrease in its ductility (referring to the zinc); and at that time such was my belief as the result of the experiments and tests I had theretofore made. My more recent experiments have led to the discovery that the ductivlity (or more correctly the plasticity) of the Zinc increases as the. temperature of extrusion is raised until a point is reached which approaches too closely to the melting temperature of the zinc, at which extrusion ceases to be possible. The discovery of this fact has 'resulted from numerous experiments accompanied by many failures. During this time I had no means of ascertaining or determining the true ductlhty curve of zinc. under extrusion conditions: this curve I have more recently been `rounding the male die in a. directionopposite 30 to the movement of the male die and While at aeeasas a temperature approximating 260 to 300 C.. in substantially the manner set forth.

2. The process of Working zinc which consists in subjecting a bla-nk to pressure between male and female dies and extrudingr it through a contracted annular space surrounding the male die in a direction opposite to the movement of the male die and While at a tempera-ture exceeding 260o C. and not inaterially exceeding 21100o C.

3. The process of working; zine which censists in subjecting a blank to pressure between male and female dies and extruding it through a contracted annular space surrounding the male die in a direction opposite to the movement of the male die and While at a temperature approxirnatingn 300 C., substantially asset forth.

4. The process of Working zinc which con sists in subjecting a blank to pressure between male' and female dies and entr-'riding it through a. contracted annular space surround ingry the male die in a direction opposite to the movement of the male die and While at a temperature materially exceeding i500 C. and not materially exceeding1 800 (C.

lin Witness whereof., l have hereunto signed my name.

Warren narices freni/Ns. 

